Science: The heating problem of lattice gauge field theory is solved

Academician Pan Jianwei and Professor Yuan Zhensheng of the University of Science and Technology of China, in cooperation with relevant researchers from heidelberg University in Germany, the University of Innsbruck in Austria, and the University of Trento in Italy, used an ultra-cold atom quantum simulator to experimentally confirm for the first time the “loss” of primary information caused by quantum multibody heating under the constraint of normative symmetry, and made important progress in solving complex physical problems using quantum simulation methods. On July 15, Beijing time, the results were published in Science.

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Schematic diagram of the thermal dynamics of the transition from non-equilibrium to equilibrium Draft: Chen Lei, Zhou Zhaoyu, Liang Yan, Yuan Zhensheng

Gauge field theory is the foundation of modern physics and is widely used in particle physics, cosmology, and condensed matter physics.

Due to its high complexity, there are still many open problems in the normative field theory system. Among them, whether the physical system described by gauge field theory can evolve from a state far away from equilibrium to thermal equilibrium is a highly concerned and challenging problem. Solving this problem will help people understand the problem of heavy nuclear collisions in high-energy physics, and will also provide a physical explanation for the formation of matter in the early Big Bang in modern cosmology.

But solving complex gauge field theory using classical computers is a recognized puzzle, and quantum simulators offer new paths to solve this problem. However, due to the complex interaction forms in lattice canonical theory and the requirement that the physical system is always under the constraint of local normative symmetry, this makes it difficult to simulate the thermal dynamics of lattice gauge field theory, so it has not been experimentally realized.

In order to solve the two main problems of the number of particles coherently regulated in the previous quantum simulator and the inability to guarantee the normative symmetry constraint, the research team of the University of Science and Technology of China developed a unique quantum regulation and measurement technology such as spin-dependent superlattices, microscopic absorption imaging, particle number resolution detection, etc., proposed and realized the deep refrigeration of the original particles in the ultra-cold atom quantum simulator, solved the problem of too many defects in the temperature of the quantum simulator, and prepared nearly 100 atomic-level large-scale quantum simulators. For the first time, an experimental simulation of the quantum phase transition process of lattice point gauge field theory using a large-scale quantum simulator is realized, and the canonical invariance of the process is verified.

On this basis, through the combination of experiments and theory, the team prepared the system to an initial state far from equilibrium, and the first experiment studied the effect of normative symmetry constraints on the thermal dynamics of quantum multibody systems, and observed the processes of different primary heating to the same equilibrium state with the same conservation amount, verified the “loss” of initial state information of quantum multibody systems caused by the heating process, and established the connection between the early non-equilibrium dynamics of canonical field theory and the final thermal equilibrium state. Important advances have been made in solving complex physics problems using large-scale quantum simulators.

The team will further use quantum simulation methods to study normative field theoretical models with higher spatial dimensions with other group symmetries, and study physical problems such as vacuum decay and dynamic topological quantum phase transitions.

The Science reviewers believe that the study “made an important contribution to the development of the field of ultracold atomic simulation lattice point gauge field theory” and “represents the frontier in the field of quantum simulation research.” (Source: China Science Daily Wang Min)

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